WO2011157087A1

WO2011157087A1 - Quick switch method and system in wireless sensor network

Info

Publication number: WO2011157087A1
Application number: PCT/CN2011/073823
Authority: WO
Inventors: 裴庆祺; 沈玉龙; 李京英; 姜晓鸿; 尹浩; 徐启建; 马建峰; 唐宏; 吴作顺
Original assignee: 西安电子科技大学; 中国电子设备系统工程公司研究所
Priority date: 2010-06-18
Filing date: 2011-05-09
Publication date: 2011-12-22
Also published as: CN101883409B; CN101883409A

Abstract

A quick switch method based on Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI) in a wireless sensor network is disclosed in the present invention, which mainly solves the problems of low switch judgment precision and long time delay in traditional switch process. The method includes the following implementing steps: 1) adopting an R value, obtained by weighting and compounding the RSSI and LQI, as a system preset parameter; 2) utilizing the R value for subnet selection, especially when a pre-addition fails, a pre-adding flow is restored rapidly, so that scanning time delay and signalling interactive times are reduced; 3) preestimating geographical positions when pre-switching, and determining a subnet covering the next moment position of a mobile user, so that times of scanning subnets and switch time delay are reduced; and 4) utilizing a progressive judgment rule so as to avoid error switch and ping-pong effect to a great extent. With the method, network capability is effectively balanced, and network life is prolonged. The method is suitable for the sensor network field which has high requirements on switch performance and is sensitive to switch time delay.

Description

The present invention claims to be submitted to the Chinese Patent Office on June 18, 2010, and the application number is 201010204178.X, and the invention name is "rapid switching method based on RSSI and LQI in wireless sensor networks". Priority of Chinese Patent Application, the entire contents of which is incorporated herein by reference.

Say

Technical field

The invention relates to the field of short-range wireless communication, in particular to a handover scheme of a mobile user in a clustering model of a wireless sensor network, which is specifically a signal strength indicator (RSI) and a link quality indicator index (LQI) in a wireless sensor network. (Link Quality Indi Cator) Fast switching method and system for applications that require high handover performance, low latency, and low power consumption for mobile users. Background technique

Wireless sensor network is a brand-new information acquisition platform. It has the advantage of being incomparable with other networks in information acquisition. It can monitor and collect information of various monitoring objects in the network distribution area in real time to achieve complex target within specified range. Detection and tracking can greatly compensate for the shortcomings of wireless network information collection. It has the characteristics of rapid deployment and strong resistance to destruction, and has broad application prospects.

Wireless sensor networks are made up of a large number of low-cost micronodes, which are typically battery-powered and work long-term in an unattended environment, often without replacing the battery. This requires efficient management and use of resources during wireless sensor network operation, reducing energy consumption, maximizing network lifetime and ensuring network connectivity for maximum long working hours.

A wireless sensor network consists of a sensor node, a subnet cluster head node, and a user. A large number of sensor nodes are deployed in the monitoring area and set up a network. The use of mobile-capable nodes to actively collect information can reduce the number of hops from the sensor nodes to the cluster head nodes, thereby saving energy, and can actively collect information in each subnet. Ensure network connectivity. Therefore, research on the mobility management of nodes and the manner of handover are introduced.

The traditional wireless sensor network mobile switching method has the following steps: First, the signal strength indicator RSSI is used as the handover criterion, and compared with the system preset parameters. If the system threshold is reached, the inter-subnet is started. Switching; the second step, scanning all subnets in the sensor network, selecting the subnet with the best performance as the switcher The third step is to complete the switch between subnets. If the switch fails, the connection is directly disconnected.

In the process of implementing the present invention, the inventors have found that the above conventional wireless sensor network mobile switching method has at least the following disadvantages:

1) Using only the signal strength indicator, RSSI, as the decision criterion for handover, can result in false switching or frequent switching. Since the RSSI is greatly affected by the environment, and sometimes the RSSI change is not caused by the mobile user moving away from the cluster head node, or because multiple mobile users compete for channels or signal interference between multiple nodes, so only rely on RSSI as a reference method for decision criteria often results in false switching or frequent switching, which not only wastes a lot of network resources, but also increases the packet loss rate and network throughput. In extreme cases, service may also occur for a long time. The situation of the interruption.

2) When it is determined that a handover is required, the mobile user needs to scan all the subnets during the scanning phase, obtain the information therein, and decide which subnet to switch to, which causes a waste of time. However, the reality is that the subnet to be accessed by the mobile user only needs to be selected among several adjacent subnets. Scanning all subnets not only causes waste of time, but also the delay caused by the scanning phase is the longest, which reaches The entire switching delay is about 90%.

3) If the mobile node fails to switch for some reason, it will directly disconnect and restart the entire handover process, which will not only increase network energy consumption, reduce network lifetime and generate frequent signaling interactions, but also provide Service disruption, especially for unrealistic consequences for businesses with high real-time requirements. Summary of the invention

The object of the present invention is to overcome the above-mentioned shortcomings of the prior art, and to provide a fast switching method and system based on a signal strength indicator index RSSI and a link strength indicator index LQI in a wireless sensor network, so as to reduce scan delay, handover delay and Data packet loss rate, increase network throughput and extend network lifetime.

In order to achieve the above object, the present invention provides a fast switching method based on RSSI and LQI in a wireless sensor network, including:

After the mobile user enters the wireless sensor network, the signal strength indicator index RSSI and the link quality indicator index LQI information of the cluster head nodes of each subnet are obtained, and the signal strength indicator index RSSI and the link quality indicator index LQI information of each subnet are obtained. Calculate the R value of each subnet, select the first subnet to be joined according to the R value of each subnet, and send an association request;

The cluster head node of the first subnet determines, according to the association request, that the mobile user is allowed to join the subnet, and the mobile user accesses the first subnet;

After the mobile user accesses the first subnet, the cluster head node of the first subnet acquires a signal strength indicator The RSSI and the link quality indicator metric LQI value are generated, the location information of the mobile user is obtained according to the ^, and the mobile user's next time position is predicted, and whether the handover process is triggered is determined; if yes, according to the prediction information The location information of the mobile subscriber is acquired at the next moment, and the signal strength and link quality information of the cluster head nodes of each new subnet covering the area are obtained, and the values of the subnets are calculated, and the second subnet to be joined is selected according to the value. And send an association request;

The cluster head node of the second subnet decides to allow the mobile user to access according to the association request, the mobile user accesses the second subnet, and disconnects from the first subnet.

The implementation steps of the method include the following:

(1) The mobile user enters the wireless sensor network to send a scan request, and then obtains the signal strength and link quality information of the cluster head nodes of each subnet through the active scan response, and the signal strength and link quality information of each subnet, Calculate the R value of each subnet, store these R values in the register, and then select the subnet with the largest R value from the register as the subnet to be joined, and send the association request;

(2) The subnet cluster head node decides whether to allow the user to join the subnet according to the user mobility status, the requested service type, and the current subnet resource information in the user association request; if the user is allowed to join the subnet, go to the step (3), otherwise, the R value is searched from the register second only to the subnet of the subnet used as the available subnet, and the association request is sent;

(3) The subnet cluster head node sends an association response to the user requiring access to the subnet;

(4) The user submits a bandwidth usage request to the sub-cluster head node according to the specific conditions of the current service, including the number of used time slots and the usage time;

(5) After receiving the bandwidth request from the user, the sub-cluster head node determines whether to approve the application according to the current status of the subnet; if the subnet provides the resource within the capability, the application is approved and the application is successfully sent to the user. In response, go to step (6); if the ability of the subnet to provide resources is exceeded, send the maximum bandwidth information that the current subnet can provide to the user, and go to step (8);

(6) When the user receives the application and successfully responds, the user starts to use the subnet resource, that is, accesses the subnet, and proceeds to step (8);

(7) If the user receives the maximum bandwidth information, it determines whether to join the subnet according to the current traffic volume. If the maximum bandwidth provided can meet the requirements of the service, then choose to join the subnet, start using the resources of the subnet, and go to the step. (8), otherwise find the R value from the register next to the subnet of the subnet used as the available subnet, go to step (3);

(8) After the mobile user accesses the subnet, at every T time, if there is data transmission between the mobile user and the cluster head node, the cluster head node directly reads the signal strength indicator RSSI from the transmitted data frame. And the link quality indicator index LQI value, if no data transmission occurs, the mobile user sends an empty data frame to the sub-cluster cluster head node, and the signal strength indicator index RSSI and the link quality indicator index LQI value are read out from the frame. Generate ^;

(9) Using ^ to compare with a preset system threshold, if ^ is in the threshold area, the cluster head node sends a location information request to the mobile user, and after receiving the request, the mobile user sends the location information to the cluster head node. Go to step (10); Otherwise, go to step (8);

(10) After receiving the location information of the mobile user, the cluster head node predicts the location of the next moment of the user, and determines whether the handover process is triggered by the location information of the time of the mobile node; if the handover is triggered, the process proceeds to step (11). Otherwise go to step (8);

(11) The cluster head node of the atomic network sends an active scan to the cluster head nodes of each new subnet covering the area according to the location information of the user at the next moment in the prediction information; and acquires the cluster head nodes of each new subnet through the active scan response Signal strength and link quality information, and calculate the value of each subnet, store it in the register, and then select the subnet with the largest value from the register as the subnet to be joined, and send the association request;

(12) The atomic network cluster head node sends an association request to the new subnet cluster head node according to the mobile user type, the motion state and the service type, and proposes a bandwidth request;

(13) The new subnet cluster head node decides whether to allow the user to join its subnet according to the bandwidth request in the association request; if the user is allowed to join the subnet, go to step (14); otherwise, look up the value from the register. After the subnet that uses the subnet is the available subnet, send the association request and repeat step (11);

(14) The new subnet cluster head node decides whether to allow the mobile node to access according to the maximum bandwidth that can be provided by itself; if access is allowed, the atomic network cluster head node notifies the user to switch to the new subnet, and proceeds to the step ( 15); Otherwise, the value of the ^ value from the register is second only to the subnet of the subnet used as the available subnet, go to step (12);

(15) If the user gets the command to switch, directly access the new subnet, start using the subnet resources and disconnect the original subnet;

(16) After the user accesses the new subnet, if the atomic network cluster head node still stores the user's data, the atomic network cluster head node sends the data to the new subnet cluster head node, which is handed over to the user;

(17) If all the new subnets in the coverage area are traversed and the user's request is not met, the user disconnects from the original subnet and switches using the traditional hard handover mode.

The invention also provides a fast switching system based on RSSI and LQI in a wireless sensor network, comprising: a mobile user, after entering the wireless sensor network, acquiring a signal strength indication index RSSI and a link of a cluster head node of each surrounding subnet The quality indicator index LQI information, and the signal strength indicator index RSSI and the link quality indicator index LQI information of each subnet are used to calculate the R value of each subnet, and the first sub-join to be added is selected according to the R value of each subnet. Networking, and sending an association request, accessing the first subnet after being allowed;

a cluster head node of the first subnet, configured to receive the association request sent by the mobile user, determine, according to the association request, that the mobile user is allowed to join the subnet, and the mobile user accesses the first After the subnet, obtaining the signal strength indicator index RSSI and the link quality indicator index LQI value, generating ^, obtaining the location information of the mobile user according to ^, and Predicting the location of the next moment of the mobile user, determining whether the handover process is triggered; if yes, obtaining the signal strength of the cluster head nodes of each new subnet covering the area according to the location information of the mobile subscriber at the next moment in the prediction information Link quality information, and calculating the value of each subnet, selecting a second subnet to be joined according to the value, and sending an association request;

The cluster head node of the second subnet is configured to allow the mobile user to access the second subnet according to the association request sent by the cluster head node of the first subnet.

The present invention has the following advantages over the prior art:

(1) The present invention uses the R value weighted by the signal strength indicator index RSSI and the link quality indicator index LQI as the system preset parameter, instead of using the RSSI as the system preset parameter in the conventional sense, the accuracy is The aspect LQI is slightly higher than the RSSI, and the two are indicators indicating different categories. Therefore, using this method can greatly improve the accuracy and avoid mis-switching.

(2) After obtaining the signal strength and link quality information of the cluster head nodes of each subnet by the active scanning response, the present invention calculates the R values of each subnet and sorts them into registers according to the order from largest to smallest. Then, subnet selection by each R value can effectively balance the network energy and prolong the network life; especially when the selection of the pre-join subnet and the pre-switch subnet fails, the entire pre-join or pre-handover can be quickly restored. The process, without having to disconnect the network and then rescan, can greatly reduce scan latency, reduce signaling interactions, and reduce overall system overhead.

(3) The present invention adopts the prediction of the geographical position in the pre-handover, and can accurately determine the subnet covering the position of the mobile node at the next moment, thereby greatly reducing the number of scanning subnets; The total handover delay is 90%, so the handover delay can be greatly reduced, and the service with higher real-time requirements can provide better service.

(4) The present invention uses a progressive decision criterion for handover decision. The first condition is to determine whether ^ is within the system preset threshold area, and after the first condition is reached, the second condition is triggered, and the second condition is judgment. Whether the moving position of the mobile node at the next moment exceeds the coverage of the atomic network, and once the coverage of the atomic network is exceeded, the handover is triggered. By using the progressive decision criterion in the present invention, the accuracy of the handover decision can be greatly improved, and false handover and "ping-pong effect" can be avoided. DRAWINGS

1 is a schematic structural diagram of a wireless sensor network used in the present invention;

2 is a general flowchart of the present invention for implementing fast switching;

3 is a sub-flow diagram of the present invention for pre-joining using R values in the process of implementing fast handover;

4 is a sub-flow diagram of the present invention for performing handover using a progressive decision criterion in implementing a fast handover procedure; FIG. 5 is a schematic diagram of a conventional mobile handover procedure;

FIG. 6 is a schematic structural diagram of a fast switching system provided by the present invention. detailed description

In order to make the objects, the technical solutions and the advantages of the present invention more apparent, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

The invention will be further described below in conjunction with the accompanying drawings.

As shown in Fig. 1, the network structure used by the present invention is composed of a wireless sensor common node, a subnet cluster head node, and a mobile user. The wireless sensor common node collects the information of the physical environment and transmits the information to the sub-cluster head node through the wireless link; the sub-cluster head node is responsible for merging the received information and rationally allocating the internal resources of the subnet; Inject queries and gather information into the network. The subnet cluster head nodes are connected together by a wired network or a wireless network, and the subnets are combined to form a flexible and scalable wireless sensor network. This network structure provides a variety of data services and applications, and supports multiple mobile users to use network resources at the same time.

The mobile user in the embodiment of the present invention refers to a mobile node, which may be a mobile terminal, and is referred to as a mobile user for ease of understanding.

The present invention provides a fast switching method based on RSSI and LQI in a wireless sensor network, including: S1: After a mobile user enters a wireless sensor network, acquires a signal strength indicator of a cluster head node of each surrounding subnet.

The RSSI and the link quality indicator index LQI information are calculated by the signal strength indicator index RSSI and the link quality indicator index LQI information of each subnet, and the R value of each subnet is calculated, and the R value of each subnet is selected to be added. The first subnet, and send an association request;

S2: the cluster head node of the first subnet decides to allow the mobile user to join the subnet according to the association request, and the mobile user accesses the first subnet;

S3: After the mobile user accesses the first subnet, the cluster head node of the first subnet obtains the signal strength indicator index RSSI and the link quality indicator index LQI value, generates ^, obtains the location information of the mobile user according to the ^, and predicts the movement. The next time position of the user determines whether the handover process is triggered; if yes, the signal strength and link quality information of the cluster head nodes of each new subnet covering the area are obtained according to the location information of the mobile subscriber at the next moment in the prediction information. And calculating the R" value of each subnet, selecting the second subnet to be joined according to the value, and sending an association request;

S4: The cluster head node of the second subnet decides to allow the mobile user to access according to the association request, and the mobile user accesses the second subnet and disconnects from the first subnet.

Referring to FIG. 2, the present invention provides a fast switching method based on RSSI and LQI in a wireless sensor network, and the specific implementation steps are as follows:

Step 1: The mobile user enters the wireless sensor network and obtains network information through an active scan request. Step 2: Each sub-cluster head node sends an active scan response to the mobile user.

Step 3: The mobile user compares the received active scan response to determine the subnet to join, and sends an association request to the cluster head node of the subnet.

Referring to Figure 3, the specific implementation steps of this step are as follows:

3a) The mobile user obtains the signal strength indicator index RSSI and the link quality indicator indicator LQI of each subnet from the received active scan response;

3b) The signal strength indicator index RSSI and the link quality indicator index LQI of each subnet are generated by the following formula

R:

R = w, xRSSI + w ₂ xRSSI _ L where RSSI is the measured signal strength indicator of each subnet, and RSSI_L is the same as RSSI derived from the measured link quality indicator LQI value of each subnet. value, is the weight of RSSI, _RSSI _ _L ^ is the weight, and ^ and the values determined by the distance between the mobile user and the sub-networks.

3c) After calculating the R values of each subnet, sort them into Rl>R2>R3> > Rn in the order of largest to smallest and store them in the register;

3d) Select a subnet with an R value of Rm from the register as a pre-joined subnet, where Rm is the largest value of Rl, R2, ..., Rn that has not been selected;

3e) Send an association request to the cluster head node pre-joining the subnet.

Step 4: The subnet cluster head node determines whether to allow the mobile user to join the subnet according to the user mobility status, the requested service type, and the current subnet resource information in the mobile user association request. The mobile user's mobile state is divided into a high-speed motion state, a medium-speed mobile state, and a low-speed mobile state; the mobile user's service type is divided into real-time service and non-real-time service. If the mobile user is allowed to join the subnet, go to step 5; otherwise, look for the available subnet from the register and go to the send association request in step 3. The specific implementation method is as shown in Figure 3:

3f) If the mobile subscriber is not allowed to join the subnet, select the subnet with the R value of TM+ from the register as the pre-joined subnet; then go to the send association request in step 3. Among them, is the maximum value that has not been selected currently in Rl, R2, ..., Rn, that is, the largest value among the unselected values smaller than Rm.

Step 5: The subnet cluster head node returns an association response to the mobile user.

Step 6: The mobile user submits a bandwidth usage request to the sub-cluster head node according to the specific situation of the current service, including using the number of slots and the usage time;

Step 7: After receiving the bandwidth usage request of the mobile user, the sub-cluster head node determines whether to approve the bandwidth usage application according to the current status of the subnet. If the subnet provides the resource within the capability of the subnet, the bandwidth usage application is approved. And moving to The user sends a successful application response, go to step 8; if the ability to provide resources beyond the subnet is exceeded, send the maximum bandwidth information that the current subnet can provide to the mobile user, go to step 9;

Step 8: The mobile user starts to use the subnet resource according to the information that the bandwidth usage request is approved by the received cluster head node, and proceeds to step 10;

Step 9: After receiving the maximum bandwidth information, the mobile user determines whether to join the subnet according to the current traffic. If the maximum bandwidth provided can meet the requirements of the service, then choose to join the subnet, start using the resources of the subnet, and go to Step 10; Otherwise, look up the available subnets from the register, and go to the sending association request in step 3. The specific implementation method is as shown in Figure 3:

3f) If the mobile user is not allowed to join the subnet, select the subnet with the R value of TM+2 as the pre-joined subnet from the register; where "^ is currently not selected in _R1 , _R2 , ..., Rn The maximum value, which is the largest of the individual unselected values smaller than ^J ^".

3g) Then go to the pre-joined subnet to send the association request in step 3.

Step 10: After the mobile user accesses the subnet, every time period T, if there is data transmission with the cluster head node of the subnet, the cluster head node directly reads the RSSI and LQI values from the transmitted data. If there is no data transmission in the subnet, after the mobile user sends an empty data frame, the cluster head node reads the RSSI and LQI values from the received null data frame, and generates the following formula:

R' = w,' X RSSI' + w ₂ ' X RSSI _ l! where RSS^ is the measured signal strength indicator of the mobile user, W^^ - is the measured link quality indicator of the mobile user The value of the index LQI value derived from the RSSI is the weight of the weight, w ₂ ' is the weight of -, and the value of ^^ and ¹ ^ is determined by the distance between the sub-cluster head node and the mobile user. The period T can be preset according to needs, for example, the default is 0.5s, and then dynamically adjusted according to the motion state of the mobile user. If the moving speed of the mobile user is faster, the value of the period T can be shortened, if the moving speed of the mobile user Slower, you can extend the value of period T;

Step 11: Use ^ to compare with the preset system threshold area, if ^ is in the threshold area, go to step 12; if ^ is not in the threshold area, go to step 10;

Step 12: The cluster head node sends a request to the mobile user, requesting the mobile user to send its current location information. Step 13: After receiving the location sending request, the mobile user sends location information to the atomic network cluster head node; wherein, the atomic network cluster head node It refers to the cluster head node of the subnet where the mobile user is currently located, that is, the subnet cluster head node involved in the above steps. In order to distinguish the new subnet cluster head node after the handover, it is called the atomic network cluster head node.

Step 14: After receiving the location information of the mobile user, the original cluster head node starts a second-order AR prediction algorithm to predict the mobile user. Next moment position ( ,

And according to ( "_^*)) ^{2 +} « _ 3^)) ² 〉 ² , judge whether the switching process is triggered, where ^XW , ^W represents the plane position information of the cluster head node of the current subnet, and r represents the current subnet The coverage radius of the cluster head node, if the switch is triggered, go to step 15; otherwise, go to step 10. The above steps 10 to 14 are as shown in FIG.

Step 15: The atomic network cluster head node sends an active scan request to each new sub-network cluster head node covering the area according to the location information of the mobile user at the next moment in the prediction information.

Step 16: Each sub-cluster head node sends an active scan response to the cluster head node of the atomic network.

Step 17: The atomic network cluster head node determines a new subnet to be joined by the mobile user according to the received active scan response, and sends an association request to the cluster head node of the new subnet.

The specific implementation method of this step is shown in Figure 3:

3a) The atomic network cluster head node obtains the signal strength indicator index RSSI and the link quality indicator index LQI of each new subnet from the received active scan response;

3b) Calculate the signal strength indicator index RSSI and the link quality indicator index LQI of each new subnet using the following formula

R" = < X RSSI" + w ₂ " X RSSI _ i!' where R^W^ is the measured signal strength indicator for each new subnet, W^^- is the actual new subnet The value of the link quality indicator LQI value derived from the RSSI is the weight of ^^^, which is the weight of ^RSSI- ^, and the values of ¹ and ¹ ^" are determined by the cluster head node of the atomic network. The distance between the cluster head nodes of each new subnet is determined.

3c) The calculated R" values of each subnet are sorted into ^R 〉 ^R ' 〉...〉 ^R "« and stored in the register in descending order;

3d) Select the subnet with the R ¹¹ value ^R ' from the register as the pre-joined new subnet, where ^R ' is the largest value that has not been selected in ^R W ', ^Rl1 ";

3e) Send an association request to the cluster head node of the new subnet to be pre-joined.

Step 18: The new subnet cluster head node determines whether to allow the mobile user to join the subnet according to the user mobility status, the requested service type, and the current subnet resource information in the association request, if the mobile user is allowed to join the subnet, then Go to step 19; otherwise, look up the available subnets from the register and send the association request. The specific implementation method is as shown in Figure 3:

3f) If the mobile user is not allowed to join the subnet, select the subnet with the R ¹¹ value d from the register as the pre-joined new subnet; where ^ ^ is ^ ^ ···^"" is not currently selected The maximum value that has passed, that is, the largest value among the smaller unselected values. 3g) Then go to step 17 to send an association request to the pre-joined new subnet.

Step 19: The new subnet cluster head node sends an association response to the atomic network cluster head node.

Step 20: The cluster head node of the atomic network proposes a bandwidth usage application to the cluster head node of the new subnet according to the specific situation of the current service of the mobile subscriber, including using the number of slots and the usage time.

Step 21: After receiving the bandwidth usage request of the cluster head node of the atomic network, the cluster head node of the new subnet determines whether to approve the application according to the current status of the subnet, and if the capability of the subnet is provided, the bandwidth usage application Approved, and send a successful application response to the cluster head node of the atomic network, go to step 22; if the ability of the subnet to provide resources is exceeded, send the maximum bandwidth information that the current subnet can provide to the cluster head node of the atomic network, go to the step twenty three.

Step 22: The atomic network cluster head node proceeds to step 24 according to the bandwidth usage request approval information sent by the new subnet cluster head node.

Step 23: After receiving the maximum bandwidth information, the cluster head node of the atomic network determines whether to join the new subnet according to the current traffic volume. If the maximum bandwidth provided can meet the requirements of the service, then select to join the new subnet, and go to the step. 24; Otherwise, look up the available subnet from the register, and then go to the send association request in step 17, the specific implementation method is as shown in Figure 3: 3f) If the mobile user is not allowed to join the subnet, the value selected from the register The subnet of ^ is the pre-joined subnet; where, is the maximum value currently not selected in ^, ^^..., ^", that is, the largest value among the smaller unselected values.

3g) Then go to step 17 to send an association request to the pre-joined subnet.

Step 24: The atomic network cluster head node notifies the mobile user to switch to the subnet covered by the new subnet cluster head node.

Step 25: After the mobile user accesses the new subnet, start using the subnet resources of the new subnet and disconnect from the atomic network. Step 26: After the mobile user accesses the new subnet, if the atomic network cluster head node still has the data of the mobile user, the atomic network cluster head node sends the data to the new subnet cluster head node, and the data is forwarded to the mobile user. .

Step 27: Traverse all new subnets in the coverage area. If the mobile user's request is not met, the mobile user disconnects from the atomic network and switches using the traditional hard handover mode.

The traditional hard handover mode is shown in the handover process in FIG. 5, and the present invention is not described too much.

Referring to FIG. 6, the present invention also provides a fast switching system based on RSSI and LQI in a wireless sensor network, including:

After entering the wireless sensor network, the mobile user 601 obtains the signal strength indicator index RSSI and the link quality indicator index LQI information of the cluster head nodes of each subnet, and the signal strength indicator index RSSI and link quality of each subnet Indicating the indicator LQI information, calculating the R value of each subnet, selecting the first subnet to be joined according to the R value of each subnet, and sending an association request, and accessing the first subnet after being allowed; The cluster head node 602 of the first subnet is configured to receive an association request sent by the mobile user, determine, according to the association request, the mobile user to join the subnet, and obtain the signal strength indicator after the mobile user accesses the first subnet. The RSSI and the link quality indicator index LQI value, generate ^, obtain the location information of the mobile user according to ^, and predict the mobile user next time position, determine whether the handover process is triggered; if yes, move according to the next time in the prediction information The location information of the user obtains the signal strength and link quality information of the cluster head nodes of each new subnet covering the area, calculates the value of each subnet, selects the second subnet to be added according to the value, and sends an association request. ;

The cluster head node 603 of the second subnet is configured to allow the mobile user to access the second subnet according to the association request sent by the cluster head node of the first subnet.

The method described in the method embodiment of the present invention may be performed in the foregoing system, and details are not described herein again.

The fast switching method and system based on RSSI and LQI in the wireless sensor network provided by the invention has the following advantages compared with the prior art:

(4) The present invention uses a progressive decision criterion for handover decision. The first condition is to determine whether ^ is within the system preset threshold area, and after the first condition is reached, the second condition is triggered, and the second condition is judgment. Whether the moving position of the mobile node at the next moment exceeds the coverage of the atomic network, and once the coverage of the atomic network is exceeded, the handover is triggered. By using the progressive decision criterion in the present invention, the accuracy of the handover decision can be greatly improved, and the false handover and the "ping-pong effect" can be avoided. All or part of the above technical solutions provided by the embodiments of the present invention may be completed by hardware related to program instructions, and the program may be stored in a readable storage medium, and the storage medium includes: a ROM, a RAM, a magnetic disk or an optical disk. Wait A variety of media that can store program code.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

Claim

A fast switching method based on RSSI and LQI in a wireless sensor network, characterized in that the method comprises:

After the mobile user accesses the first subnet, the cluster head node of the first subnet acquires a signal strength indicator

The RSSI and the link quality indicator metric LQI value are generated, the location information of the mobile user is obtained according to the ^, and the mobile user's next time position is predicted, and whether the handover process is triggered is determined; if yes, according to the prediction information The location information of the mobile subscriber is acquired at the next moment, and the signal strength and link quality information of the cluster head nodes of each new subnet covering the area are obtained, and the values of the subnets are calculated, and the second subnet to be joined is selected according to the value. And send an association request;

The fast switching method according to claim 1, wherein the method specifically includes the following steps:

(1) After the mobile user enters the wireless sensor network, it first sends a scan request, and then obtains the signal strength indication index RSSI and the link quality indicator index LQI information of the cluster head nodes of the surrounding subnets through the active scan response, and is performed by each subnet. The signal strength indicator index RSSI and the link quality indicator index LQI information, calculate the R value of each subnet, store these R values in the register, and then select the subnet with the largest R value from the register as the first to be added. Subnet and send an association request;

(2) The cluster head node of the first subnet determines whether to allow the mobile user to join the subnet according to the user mobility status, the requested service type, and the current subnet resource information in the mobile user association request; If the user joins the subnet, go to step (3). Otherwise, find the R value from the register next to the subnet using the subnet as the available first subnet, and send the association request;

(3) the cluster head node of the first subnet sends an association response to a mobile user that requires access to the subnet;

(4) The mobile user submits a bandwidth usage request to the cluster head node of the first subnet according to the specific situation of the current service;

(5) After receiving the bandwidth usage request of the mobile user, the sub-cluster head node determines whether to approve according to the current status of the subnet. The bandwidth usage request; if the subnet provides the resource capability, the bandwidth usage application is approved, and the application is successfully sent to the mobile user, and the process proceeds to step (6); if the subnet provides the resource capacity, Sending the maximum bandwidth information that the current subnet can provide to the mobile user, and proceeds to step (7);

(6) The mobile user accesses the first subnet after receiving the application successfully, and proceeds to step (8);

(7) The mobile user receives the maximum bandwidth information, and determines whether to join the first subnet according to the current traffic volume. If the maximum bandwidth provided by the first subnet can meet the service requirement, the access station Said first subnet, go to step (8), otherwise look up the R value from the register next to the subnet using the subnet as the available first subnet, send the association request, go to step (3);

(8) After the mobile user accesses the first subnet, at time T, if there is data transmission between the mobile user and the cluster head node of the first subnet, the cluster head of the first subnet The node directly reads the signal strength indicator index RSSI and the link quality indicator index LQI value from the transmitted data frame, and if no data transmission occurs, the mobile user sends an empty data to the cluster head node of the first subnet. a frame, the cluster head node of the first subnet reads out a signal strength indicator index RSSI and a link quality indicator index LQI value from the frame, and generates an R′

(9) The cluster head node of the first subnet is compared with a preset system threshold area, and if the threshold head area is within the threshold area, the cluster head node of the first subnet sends a location information request to the mobile user, After receiving the request, the mobile user sends location information to the cluster head node of the first subnet, and proceeds to step (10); otherwise, proceeds to step (8);

(10) after receiving the location information of the mobile user, the cluster head node of the first subnet predicts the next time position of the mobile user, and determines whether the handover process is triggered by the location information of the mobile user at the next moment; if the handover is Trigger to go to step (11), otherwise go to step (8);

(11) The cluster head node of the first subnet sends an active scan to the cluster head nodes of each new subnet covering the area according to the location information of the mobile subscriber at the next moment in the prediction information; and obtains surrounding The signal strength and link quality information of the cluster head node of the new subnet, and calculate the value of each subnet, store it in the register, and then select the subnet with the largest value from the register as the second subnet to be joined, and Send an association request;

(12) the cluster head node of the first subnet sends an association request to the cluster head node of the second subnet according to the mobile user type, the motion state, and the service type, and proposes a bandwidth usage application;

(13) the cluster head node of the second subnet determines whether to allow the mobile user to join the subnet according to the bandwidth usage request in the association request; if the mobile user is allowed to join the subnet, go to step (14), otherwise, Find the value from the register next to the subnet using the subnet as the available second subnet, send the association request and repeat step (11);

(14) The cluster head node of the second subnet decides whether to allow mobile users to access according to the maximum bandwidth that can be provided by itself; if access is allowed, the atomic network cluster head node notifies the mobile user to switch to the new subnet. , go to step (15); no Bay|J, then look up the value from the register next to the subnet using the subnet as the available second subnet, go to step (12);

(15) the mobile user obtains a command to perform handover, accesses the second subnet, and disconnects from the first subnet;

(16) after the mobile user accesses the second subnet, if the first subnet cluster head node still stores data of the mobile user, the cluster head node of the first subnet sends the data to The cluster head node of the second subnet is handed over to the mobile user;

(17) If all the new subnets in the coverage area are traversed and the request of the mobile user is not satisfied, the mobile user disconnects from the first subnet and switches using the traditional hard handover mode.

The fast switching method according to claim 1 or 2, wherein the R value of each subnet is calculated by the signal strength and link quality information of each subnet, and is calculated by the following formula:

R = w, xRSSI + w ₂ xRSSI _ L where RSSI is the measured signal strength indicator of each subnet, and RSSI_L is the same as RSSI derived from the measured link quality indicator LQI value of each subnet. value, is the weight of RSSI, _RSSI _ _L ^ is a weighting value and the value ₂ ^, and is determined by the distance between the mobile user and the sub-networks.

4. The fast switching method according to claim 2, wherein the storing the R values in the register according to step (1) is sequentially sorting and storing the R values of each subnet from large to small. .

The fast switching method according to claim 2, wherein the user movement state in the step (2) comprises a high speed motion state, a medium speed movement state, and a low speed movement state.

The fast handover method according to claim 2, wherein the user service type described in step (2) comprises real-time services and non-real-time services.

The fast handover method according to claim 2, wherein the cluster head node in step (8) directly reads the signal strength indicator index RSSI and the link quality indicator index LQI from the transmitted data frame. The value, generated ^, is calculated using the following formula:

R' = wl X RSSI ¹ + w ₂ ' x RSSI _ where, is the measured signal strength indicator of the mobile user, W^^ - is derived from the measured link quality indicator LQI value of the mobile user The value of the RSSI is the weight of the class, w ₂ ' is the weight of RSSI _ l!, and the value of ^^ and ¹ ^ is determined by the distance between the sub-cluster head node and the mobile user.

The fast handover method according to claim 2, wherein the predicted _λ mobile subscriber next time position in step (10) is predicted by the second-order AR prediction algorithm to predict the location of the mobile subscriber at the next moment. Coordinates ( , ).

The fast switching method according to claim 2, wherein, in the step (10), whether the switching process of the position information _λ by the mobile user next time _λ is triggered is determined by using the following formula:

(X (t) - x(t)) ² + (Y(t) - y(t)† >

Where _Λ Χ « , ί^) represents the plane coordinate information of the cluster head node of the current subnet, _r represents the coverage radius of the cluster head node of the current subnet, and ^ is the coordinates of the time position of the mobile user.

The fast switching method according to claim 2, wherein, in step (11), the signal strength and link quality information of each new subnet are used to calculate the value of each subnet, and the following formula is adopted. Calculation:

R" = w "xRSSl" + w " xRSSI _ ΐ!' where R^W^ is the measured signal strength indicator for each new subnet, W^^- is the chain of each new subnet measured The value of the road quality indicator LQI value derived from the RSSI is the weight of ^{^^^} , which is the weight of ^RSS1 , and the values of ^^ and ¹ ^ are determined by the atomic network cluster head node and each new subnet. The distance between the cluster head nodes is determined.

11. A fast switching system based on RSSI and LQI in a wireless sensor network, wherein the system comprises:

The mobile user, after entering the wireless sensor network, obtains the signal strength indicator of the cluster head node of each surrounding subnet

The RSSI and the link quality indicator index LQI information are calculated by the signal strength indicator index RSSI and the link quality indicator index LQI information of each subnet, and the R value of each subnet is calculated, and the R value of each subnet is selected to be added. The first subnet, and send an association request, and access the first subnet after being allowed;

a cluster head node of the first subnet, configured to receive the association request sent by the mobile user, determine, according to the association request, that the mobile user is allowed to join the subnet, and the mobile user accesses the first After the subnet, obtaining the signal strength indicator index RSSI and the link quality indicator index LQI value, generating ^, obtaining the location information of the mobile user according to the ^, and predicting the next time position of the mobile user, determining whether the handover process is triggered If yes, the signal strength and link quality information of the cluster head nodes of each new subnet covering the area are obtained according to the location information of the mobile subscriber at the next moment in the prediction information, and the values of the subnets are calculated according to the value. Selecting a second subnet to be added, and sending an association request; a cluster head node of the second subnet, configured to allow the mobile user to access the location according to an association request sent by the cluster head node of the first subnet Said second subnet.